Overview:To learn more about the earth's
surface, try collecting different kinds of soils in your own community. Soil is
the name given to the material found above the solid rock of the earth. It consists
of particles worn from rock mixed with decaying animal and vegetable matter. There
are some easily recognizable common types of soil, clay, gravel, and sand, which
differ in texture. Some are made up of finer particles than others and in some
the particles are more closely packed than in others. For these reasons, different
types of soil differ in the way they look, feel, hold water, etc. The following
activity will make students more familiar with the different types of soil.

Objectives:1. Students will use the
Digital Atlas of Idaho.
2. Students will learn how to collect and identify soils.
3. Students will do an outdoor activity.

Procedure:Use the Soil sections of
the Digital Atlas. To get there: Click on Atlas Home, Geology, Basics, then
on FAQ. Be sure to click
on the What is Soil link and read these pages for some background information
on soil. To get there: Click on Idaho Overview, then on Soils.
These pages contain detailed information on different types of soil. Be sure
to click on the Soil Taxonomy Key to observe characteristics of different types
of soil.

1. Fill
clear plastic containers or glass jars with samples of sand, silt, clay, and
loam (see below for definitions). It would be interesting to add to your collection
samples of soil from various parts of the country, gathered during a vacation
trip. Make labels for the containers, noting all the classification and location
information about each sample as discussed below.

2. Soils
are made up of three kinds of particle groups or 'separates', as they are called.
These separates are sand, silt, and clay. But no soil found in nature consists
completely of one of these separates. It is always a combination of separates.
These combinations are called classes. You will want to try to identify the
soil class to which each of your samples belongs. In a laboratory, a scientist
would add a large amount of water to the sample, the grains would separate out
and the proportions of sand, silt, and clay could be recorded. You will have
to depend on cruder classification methods. The best way to do it is by texture.
To determine texture, you must moisten the sample and rub it between your fingers.
You can identify the sample by comparing the way it feels with the list of classes
below:

Silt-A
fine grained, unconsolidated sediment with particles intermediate in size
of sand and claySand-A mixture but largely sand; coarse and gritty to the touch; separate
particles are easily seen; doesn't hold together when moist but falls apart
in your hands as separate grains. Made up of large grainsLoamy sand-Holds together a little when slightly moist. Sandy loam-Holds together when moist but hardly makes any smear on
your fingers. Loam-Makes a rough smear and feels sandy. A rich soil composed of sand,
clay, and organic material.Silt loam-Makes some smear when moist but doesn't rub out thin like
clay before becoming rough and broken.Clay loam, Silty clay loam and Silty clay-Makes smears
midway between silt loam and clay when moist; are easily crushed fine between
fingers when dry; particles are difficult to distinguish. Clay-A mixture but largely clay; sticky and plastic when wet, and hard
and difficult to crush when dry; when moist and rubbed between fingers, makes
a smooth, thin, continuous smear; very small separate particles can be seen
only under microscope.

3. You will
also notice differences in the colors of your samples. They may range from black
through brown, red, yellow and light gray to white. Colors do not necessarily
have any connection with soil classes but you certainly should add color to
the class name so that samples are described as "red sandy loam" or
"white clay," etc. For more information on colors of soil, click on
the Soils link above.

4. Finally,
add the name of the town or city near which the soil was found. Scientists use
these place names to describe soils, so you might read about "Miami sandy
loam" or "Des Moines black clay loam."

Lesson plan by Dr. Helen Challand
and Elizabeth Brandt with permission from Science Activities from A to Z.Idaho
Achievement Standards (as of 7/2001) met by completing this activity:
351.01.02.03
352.01